Well, it's been about four months since the big announcement and the world hasn't fallen to pieces yet. Tiger Woods' initial confessions aside, Google's December kickoff of personalized search results for all users based on past behavior, regardless of whether they had ever opted in for such a feature, led to a whole new slew of claims that SEO is dead.
My experiences could be completely wrong here, but in observing natural results across dozens of brands that are actively engaged in an SEO campaign, and a fair number that aren't, there haven't been a whole lot of changes from this supposedly groundbreaking move on Google's part. Those who were making the effort continued to climb, and those who chose to leave SEO as a "someday" priority, largely stayed where they were or dropped as we would expect. There are neither cries of anguish from Webmasters, nor praise of any results changes from users.
Regardless of Google's success or lack thereof, user behavior will become a truly significant part of the algorithm some day. Even if Google or Bing masters it first, we still might not hear about it until it has already been released. So, how can you prepare your Web site and your brand to fit into the current incremental change and be prepared to thrive in such a new environment?
Many of the Same Rules Will Still Apply
Any new rules will be built on top of the old rules. No matter the other factors, if your site can't be found or read by search engines you'll never win for any terms. If your site doesn't use the word "shoes" anywhere, don't expect to perform well for the term "shoes" in rankings.
Also: links, links, links!
Getting the fundamentals in order will put you in a position where you'll only need to make minimal adjustments to meet any challenge.
Content Specificity and Keyword Choice
Today, you'll often see the front page of a site ranking for a category-level term. For example, Google the word "sweaters" and note the front page of JCrew.com toward the top. From what we've seen from Caffeine, Google is much more inclined to require a page to be very specific to sweaters in order to appear here.
Sometimes this means a site's rankings stay the same and it's just a shift in landing page. Sometimes it includes a drop (or increase) in rankings. Likewise, any algorithm that attempts to target user behavior will be looking for the most specific content to match to a query.
Deeper merchandising, more specific bucketing of products or topics into categories, and other opportunities to build specificity into your site -- and thus your keyword targeting -- could mean the difference between showing up in the search results on the first page or the third page.
Attract Clicks and Remember the End User
Click-through is already a factor in Google's personalized search, and will only get bigger. The easiest way to improve CTR is with targeted title tags and meta descriptions for each page. Let users know that they'll find what they're looking for if they click-through and give them a call to action.
Assuming your fundamentals are taken care of, your next big project should be to add microformatting to products, locations, events and anything you can find. Semantic markup allows you to enhance your SERPs in Google and other search engines, while also adding more detail to your pages, which communicates to engines exactly what it and your site are about. This will become even more important as engines try to discern both user intent and the content of...well...your content.
Improved usability on your site may also play a role. A user's actions after they've clicked on your result (especially whether they searched again or clicked other results after viewing your page) might become a bigger part of your site's score. Building good usability into your site will not only improve your conversion rate and customer interaction, but could help you rank better as well.
Keep Your Eye on the Ball
In the end, we have no idea what changes the search world will throw at us, only that it will become more complicated and the stakes will become higher for brands and e-commerce teams. Regardless of what Google may have in store for us, building good and readable content, targeting keywords smartly, and developing a good rapport with your customers will always be a good formula to follow.